15.00 - Row Structure for Packed64 Systems - Teradata Database

Teradata Database Design

prodname
Teradata Database
vrm_release
15.00
category
User Guide
featnum
B035-1094-015K

Row Structure for Packed64 Systems

Base table rows are stored in packed format on packed64 format systems, so they need not align on 8‑byte boundaries. Because of this, their row structure is simpler than that of equivalent base table rows on aligned row format systems (see “Row Structure for Aligned Row Format Systems” on page 755).

Note that the Row Hash value is 4 bytes wide irrespective of the number of hash buckets the system has (see “Teradata Database Hashing Algorithm” on page 225).

Packed64 Row Structure for an Nonpartitioned Primary Index Table

The following graphic illustrates the basic structure of a Teradata Database row from a table on a packed64 format system with an nonpartitioned, or traditional, primary index.

Packed64 Row Structure for a Partitioned Table

The following graphic illustrates the basic structure of a Teradata Database row from a table on a packed64 format system with a partitioned primary index:

The difference between this and the format of a nonpartitioned primary index row is the presence of a an additional 2-byte or 8‑byte partition number field, which is also a component of the RowID (PPI table rows are an additional 4 bytes wider if they also specify multi-value compression). It is this field that generates the need for a BYTE(10) data type specification for a RowID. For nonpartitioned primary index tables, the partition number is assumed to be 0, so the rowID of an nonpartitioned primary index table is also logically BYTE(10) (see “ROWID Columns” on page 800).